"dullard," 1570s, from earlier Duns disciple "follower of John Duns Scotus" (c.1265-1308), Scottish scholar of philosophy and theology supposed to have been born at Duns in Berwickshire. By 16c., humanist reaction against medieval theology singled him out as the type of the hairsplitting scholastic. It became a general term of reproach applied to more conservative philosophical opponents by 1520s, later extended to any dull-witted student.

1867, long, flowing whiskers, like those worn by actor E.A. Sothern (1826-1881) while playing Lord Dundreary, witless, indolent chief character in English dramatist Tom Taylor's play "Our American Cousin" (1858).

1790, from French, Middle Dutch or Middle Low German dune, all perhaps from Gaulish *dunom (thus related to down (n.2)). The French dune "sand hill" (13c.) is held by Diez to be an Old French borrowing from Dutch duin or some other Germanic source. Italian and Spanish duna are from French. Dune buggy attested by 1965.

The word recalls the ancient Germanic custom (reported by Tacitus) of covering underground shelters with manure to keep in warmth in winter. The meaning "animal excrement," whether used as fertilizer or not, is from late 13c.

The whole body of journeymen tailors is divided into two classes, denominated Flints and Dungs: the former work by the day and receive all equal wages; the latter work generally by the piece [1824].

Dung beetle attested by 1630s. In colloquial American English, tumble-bug. An Old English word for it was tordwifel "turd weevil."

c.1300, "great tower of a castle," from Old French donjon "great tower of a castle" (12c.), from Gallo-Roman *dominionem, from Late Latin dominium, from Latin dominus "master" (of the castle; see domain). Sense of "castle keep" led to "strong (underground) cell" in English early 14c. The original sense went with the variant donjon.

1650s, from Latin in duodecimo (folded) "in a twelfth" of a sheet, from ablative of duodecimus "twelfth," from duodecim (see dozen). Often abbreviated 12mo.; a book in which each page is the twelfth part of the printer's sheet.

late 14c., from Medieval Latin duodenum digitorium "space of twelve digits," from Latin duodeni "twelve each." Coined by Gerard of Cremona (d.1187), who translated "Canon Avicennae," a loan-translation of Greek dodekadaktylon, literally "twelve fingers long," the intestine part so called by Greek physician Herophilus (c.353-280 B.C.E.) for its length, about equal to the breadth of twelve fingers.

early 15c., from Old French duplicite (13c.), from Late Latin duplicitatem (nominative duplicitas) "doubleness," in Medieval Latin "ambiguity," noun of quality from duplex (genitive duplicis) "twofold." The notion is of being "double" in one's conduct (compare Greek diploos "treacherous, double-minded," literally "twofold, double").

late 14c., from Old French duration, from Medieval Latin durationem (nominative duratio), noun of action from past participle stem of Latin durare "harden" (see endure). Old legalese phrase for the duration popularized 1916 in reference to British enlistments in World War I.

early 14c., "harsh or severe treatment," from Old French duresse, from Latin duritia "hardness," from durus "hard" (see endure). For Old French -esse, compare fortress. Sense of "coercion, compulsion" is from 1590s.

c.1000, Dunholm "city on a hill," a merger of Old English dun "hill" (see down (n.2)) and Scandinavian holmr (see holm). The change from -n- to -r- is a result of Norman confusion (see Shrewsbury). As a breed of cattle, by 1810.

late 14c., durand, present participle of obsolete verb duren "to last, endure" (mid-13c.), from Old French durer, from Latin durare "endure" (see endure). During the day really is "while the day endures," and the usage is a transference into English of a Latin ablative absolute (compare durante bello "during (literally 'enduring') the war").

capital of Tajikistan, from Tajik dushanbe "Monday" (a compound of du "two" + Shanbe "Saturday," literally "Sabbath;" thus "two days after Saturday"); so called in reference to a regular Monday market there. Known from 1929-1961 as Stalinabad.

c.1200, dosk "obscure, to become dark," perhaps from Old English dox "dark-haired, dark from the absence of light" (cognate with Swedish duska "be misty," Latin fuscus "dark," Sanskrit dhusarah "dust-colored;" also compare Old English dosan "chestnut-brown," Old High German tusin "pale yellow") with transposition of -k- and -s-, perhaps via a Northumbrian variant (compare colloquial ax for ask). But OED notes that "few of our words in -sk are of OE origin." A color word originally; the sense of "twilight" is recorded from 1620s.

c.1200, "to rise as dust;" later "to sprinkle with dust" (1590s) and "to rid of dust" (1560s); from dust (n.). Related: Dusted; dusting. Sense of "to kill" is U.S. slang first recorded 1938 (compare bite the dust under bite (v.)).